1. Field of the Invention
The present invention relates to a lighting apparatus.
2. Description of the Related Art
Nowadays, a fiber light source formed of a combination of a small solid light source and an optical fiber is being developed. The fiber light source is used as a lighting apparatus which emits light from a distal end of a thin structure.
As such a lighting apparatus, for example, Jpn. Pat. Appln. KOKAI Pub. No. 2009-3228 presents a fiber light source apparatus (light-emitting apparatus) using a solid light source.
In the fiber light source apparatus disclosed in Jpn. Pat. Appln. KOKAI Pub. No. 2009-3228, a light guide member (optical fiber) is connected to a small solid light source, and a wavelength converting member (fluorescent material) is attached to a distal end of the light guide member. The light guide member is attached to a retaining member, and a spacer is placed between the light guide member and the wavelength converting member. The spacer includes a through hole, and a metal thin film is formed on an internal surface of the through hole. In the fiber light source apparatus, a backward emitted light emitted from the wavelength converting member toward the light guide member is reflected by a reflector formed of the metal thin film provided on the internal surface of the through hole of the spacer. Thereby, the light emitted toward the light guide member is returned toward the wavelength converting member, and thereby the illumination light quantity of the wavelength-converted light is increased.
The fiber light source apparatus disclosed in Jpn. Pat. Appln. KOKAI Pub. No. 2009-3228 includes a light-emitting element, a light guide member which guides light from the light-emitting element, a retaining member attached to at least an emitting end of the light guide member, and a wavelength converting member which is provided on the emitting side of the light guide member, absorbs at least part of the light from the light-emitting element, and converts the light into light of a different wavelength. The fiber light source apparatus has a structure in which a spacer which reflects backward emitted light emitted from the wavelength converting member is attached to a part between the retaining member or the light guide member and the wavelength converting member. By virtue of this structure, it is possible to reduce a loss of light due to incidence of light reflected or generated by the wavelength converting member on an end surface of the retaining member, and improve the light output. Thus, it is possible to improve brightness, by providing means for reflecting backward emitted light, which was not efficiently used before, toward a direction in which the light is to be output.
The above fiber light source apparatus has a structure in which the whole surface of the emitting opening of the spacer is covered with the wavelength converting member. Thus, the backward emitted light reflected by the reflector being the internal surface of the through hole of the spacer passes through the wavelength converting member, and is output to the exterior. However, the wavelength converting member generally has self-absorbability, and thus absorbs part of the wavelength-converted light which has been wavelength-converted by the wavelength converting member. This absorption reduces the light quantity of the wavelength-converted light emitted to the exterior. Thus, the structure of the above fiber light source apparatus has a problem that the wavelength-converted light from the wavelength converting member is not sufficiently used, and the light extraction efficiency is improved to a lesser degree than expected.